A type of network Protocol that allows nodes to contend for network access. That is, two or more nodes may try to send messages across the network simultaneously. The ContentionProtocol defines what happens when this occurs. The most widely used ContentionProtocol is CSMA/CD, used by Ethernet. Also see CSMA/CA, polling and token passing. See also TokenRing, and the more general and related concept, DemandAssignedMultipleAccess.